The present invention relates to an electromagnetically actuated fuel injection valve for an internal combustion engine and, in particular, to an improved circuit for supplying fuel to the injection orifice of the valve itself.
As is known, valves of this type substantially comprise a casing of cylindrical form, an injection nozzle fixed to the casing and provided with at least one fuel injection orifice and a shutter member movable under the action of an electromagnet which is operable to control the passage of fuel through the injection orifice.
The movable shutter member is provided with a substantially flat active surface adapted to engage a corresponding seat of the nozzle within the interior of which the injection orifice is located.
To supply fuel to the said injection orifice from a region outside the valve there is normally provided a circuit including perforations formed in the side wall of the valve casing in a region located in the upper part of the casing itself well above the said first seat. This circuit includes a series of ducts extending from suitable holes and surfaces of various members of the valve which put the said perforations into communication with the injection orifice.
The first-mentioned circuit serves, as well as to supply fuel to the injection orifice from the said region outside the valve, also to convey to this region fuel which is not injected and which therefore must be discharged from the valve itself.
Valves of the described type have various disadvantages.
First of all, when the valve is inactive, in particular when the motor vehicle on which it is mounted remains for a long period exposed to the sun, fuel vapours form within the first mentioned fuel circuit, which makes it difficult to start the engine, and which can easily result in unburnt fuel in the exhaust. In fact, the fuel duct starting from the interior of the valve has a rather great length and comprises numerous sections of short dimensions within which fuel vapours can easily arise.
Moreover, there is a pressure drop along the said duct which reduces the fuel pressure supplied to the injection orifice, and which detrimentally influences the metering and atomisation action performed by the valve.